1. Field of the Invention
This invention relates to a method for insert molding, and more particularly to a method for producing connectors.
2. Description of the Related Art
There have been proposed various techniques for holding an insert in position in producing an insert-embedded molding.
For example, a technique disclosed by Japanese Patent Application Laid-Open Specification No. 7-88882 is as shown in FIG. 6A, which is a sectional view of a distribution box A having a connector portion a at an outer side thereof.
In this figure, denoted b is a busbar which electrically connects an upper terminal in the connector portion a to a body portion c of the distribution box A. Denoted d is a busbar which electrically connects a lower terminal in the connector portion a to the outside of the distribution box A.
This distribution box A is produced by setting the busbars b and d in a cavity E defined by an upper die B, lower die C and slide die D as shown in FIG. 6B and casting (injecting) resin into the cavity. In this instance, the busbar b is held between a projection C1 provided on the lower die C and the upper die B so as to be set in position during molding.
The insert-holding technique as mentioned above, however, is not employable where a plurality of inserts are provided in tiers extending parallel to each other, i.e., in such a case where the busbar d of the lower terminal in FIG. 6B is extended parallel to the busbar b to electrically connect to the body portion c of the distribution box A. This is because both parallel, spaced busbars b, d cannot be held in position by the projection Cl and the upper die B. If not held in position during molding, the inserts may contact each other inside the molding, and/or connecting portions cannot be obtained at positions required in the distribution box, resulting in the distribution box unreliable.
To cope with this drawback, in the above-mentioned Japanese Patent Application Laid-Open Specification No. 7-88882, a unit f as shown in FIG. 6C is provided which is separate from the distribution box A, which has a terminal e contained therein as an insert, and which is fitted in the connector portion a of the distribution box A to dispose the terminal e at a position parallel to and in tiers with the busbar b.
In this case, however, two operation of insert molding must be done to obtain a single product, which is troublesome, and since the unit f is a separate part, a fear arises that it may get out of place during the fitting of a mating connector to, or its detaching from, the connector portion a, resulting in.
A further drawback is that the conventional technique is not employable where the distribution box A requires waterproofness because the use of the projection C1 leaves a hole in the product, which may allow water to penetrate therethrough. Thus, with the conventional technique, there are no practical means for holding a busbar in position where waterproofness is required.
Further, where inserts are electrically connected busbars, the conventional technique requires a slide die such as D in FIG. 6B to prevent resin from adhering to their portions of contact with mating terminals, resulting in an increase of die production costs and in possible problem with the slide die during molding.